I would not recommend porting the heads on a motor unless you plan on running "hot". Makes no sense spending $6-1000 on port work when the optimal region where porting kicks in is in the upper realm of street crusing RPM band. Likewise, porting IMO, is best served in typical street motors running a compression ratio of 10 or above or forced induction with decent boost.

I would consider though milling the spring pads down for a stouter valvetrain similar to the RA of 67. You do not necessarily need the 1.71 installed valve height for a low compression rebuild, but can be nice if you are at or above 10.

I would base my decision on compression on a few things. Miles per year, street or highway, rear and trans.

Since we know you have a Tremec with a possible overdrive final ratio of .6 to .7 and a 3.90 gear, I (personally) would build it to 10.5 and take the sharp edges out of the chambers with a polish to reduce hot spots, recurve distributor and calibrate the carb well to further the detonation issue. I ran a 428 with polished chambered and ported 48's at a 10.9 ratio on a blend of Sunoco 94 and 10% 110. Toulene can replace 110 octane rather inexpensively.

I will be rebuilding my 400 HO soon. I decided to go with a final CR of 10.5 with a 3.55 and M-20. I'll drive it to work and around town. I do not plan on shows, or more than 3000 miles a year. I calculated that my milage will be roughly 20% less than the T/A which will result in 20% more fuel, but with additives or a blend, what is $50 a tank? Would rather have the "fun factor" myself.

Just an opinion, but these cars do sound better...different and smell better with period correct compression, cam and fuel.